The biological and chemical interactions of chemical carcinogens with cultured rodent cells will be studied. Emphasis will be placed on interactions involving DNA. Specific problems to be studied are: a) The nature of the chemical binding to DNA which is observed with many carcinogens. b) Treatments and agents which may modify the interaction of carcinogens and DNA such as metabolic inhibitors, cancer promoting agents and noncarcinogenic analogs of carcinogens. c) The effect of chemical carcinogens on homeostatic DNA repair mechanisms. d) The effect of the binding of chemical carcinogens to DNA on normal replication. e) Whether inhibition of the binding of carcinogens to DNA can be correlated with reduced probability of the cultured cells being transformed into cancer cells. f) Metabolism of chemical carcinogens which leads to binding to DNA.